The Accuracy of the Learning-Curve Cumulative Sum Method in Assessing Brachial Plexus Block Competency.

BACKGROUND: The learning-curve cumulative sum method (LC-CUSUM) and its risk-adjusted form (RA-LC-CUSUM) have been proposed as performance-monitoring methods to assess competency during the learning phase of procedural skills. However, scarce data exist about the method's accuracy. This study aimed to compare the accuracy of LC-CUSUM forms using historical data consisting of sequences of successes and failures in brachial plexus blocks (BPBs) performed by anesthesia residents. METHODS: Using historical data from 1713 BPB performed by 32 anesthesia residents, individual learning curves were constructed using the LC-CUSUM and RA-LC-CUSUM methods. A multilevel logistic regression model predicted the procedure-specific risk of failure incorporated in the RA-LC-CUSUM calculations. Competency was defined as a maximum 15% cumulative failure rate and was used as the reference for determining the accuracy of both methods. RESULTS: According to the LC-CUSUM method, 22 residents (84.61%) attained competency after a median of 18.5 blocks (interquartile range [IQR], 14-23), while the RA-LC-CUSUM assigned competency to 20 residents (76.92%) after a median of 17.5 blocks (IQR, 14-25, P = .001). The median failure rate at reaching competency was 6.5% (4%-9.75%) under the LC-CUSUM and 6.5% (4%-9%) for the RA-LC-CUSUM method (P = .37). The sensitivity of the LC-CUSUM (85%; 95% confidence interval [CI], 71%-98%) was similar to the RA-LC-CUSUM method (77%; 95% CI, 61%-93%; P = .15). Identical specificity values were found for both methods (67%; 95% CI, 29%-100%, P = 1). CONCLUSIONS: The LC-CUSUM and RA-LC-CUSUM methods were associated with substantial false-positive and false-negative rates. Also, small lower limits for the 95% CIs around the accuracy measures were observed, indicating that the methods may be inaccurate for high-stakes decisions about resident competency at BPBs.

Treatment of varicose great saphenous vein with endovenous laser alone or combined with eco-guided foam sclerotherapy: A randomized controlled trial.

Objectives: This study compares Endovenous Laser Ablation (EVLA) alone versus combined with ultrasound-guided foam sclerotherapy (UGFS) for Great Saphenous Vein (GSV) insufficiency. Methods: Sixty patients were randomly allocated to EVLA or EVLA-UGFS groups which focused on GSV occlusion rates, complications, additional treatments, and quality of life (QoL) changes. Results: Among 55 participants, the EVLA group had higher 12-month occlusion rates (92.3% vs. 75.8%, p = 0.11). Nervous injury (NI) was rarer in EVLA-UGFS (3.4% vs. 23.1%, p = 0.04). No significant difference in other complication rates (p > 0.05). QoL improved in both groups (p < 0.001). EVLA-UGFS required more subsequent procedures (24.1% vs. 7.7%, p = 0.03). Conclusions: EVLA and EVLA-UGFS effectively treat GSV insufficiency, enhancing QoL. The combined method reduces NI risk but may require more follow-up procedures.

Assessment of the learning curve of peribulbar blocks using the Learning-Curve Cumulative Sum Method (LC-CUSUM): an observational study.

INTRODUCTION: This study aimed to assess the learning curves of peribulbar anesthesia and estimate the number of blocks needed to attain proficiency. METHODS: Anonymized records of sequential peribulbar blocks performed by first-year anesthesia residents were analyzed. The block sequential number and the outcomes were extracted from each record. Success was defined as a complete sensory and motor block of the eye, and failure was defined as an incomplete block requiring supplemental local anesthetic injections or general anesthesia. Learning curves using the LC-CUSUM method were constructed, aiming for acceptable and unacceptable failure rates of 10% and 20%, and 10% probability of type I and II errors. Simulations were used to determine the proficiency limit h0. Residents whose curves reached h0 were considered proficient. The Sequential Probability Ratio Test Cumulative Sum Method (SPRT-CUSUM) was used for follow-up. RESULTS: Thirty-nine residents performed 2076 blocks (median = 52 blocks per resident; Interquartile Range (IQR) [range] = 27-78 [4-132]). Thirty residents (77%) achieved proficiency after a median of 13 blocks (13-24 [13-24]). CONCLUSIONS: The LC-CUSUM is a robust method for detecting resident proficiency at peribulbar anesthesia, defined as success rates exceeding 90%. Accordingly, 13 to 24 supervised double-injection peribulbar blocks are needed to attain competence at peribulbar anesthesia.

Surgical versus non-surgical treatment of flail chest: a meta-analysis of randomized controlled trials.

PURPOSE: Conflicting evidence exists on the choice of surgical or non-surgical treatment of flail chest injuries. We aimed to perform a meta-analysis comparing outcomes in patients presenting flail chest undergoing surgical or non-surgical treatment. METHODS: Embase, PubMed, and Cochrane databases were searched for randomized controlled trials (RCTs) comparing surgery to no surgery in patients with acute unstable chest wall injuries. We computed weighted mean differences (WMDs) for continuous outcomes and risk ratios (RRs) for binary endpoints, with 95% confidence intervals (CIs). Random effects meta-analyses were performed. Heterogeneity was assessed using I2 statistics. RESULTS: Six RCTs (544 patients) were included, and surgical treatment was used in 269 (49.4%). Compared to no surgery, surgery reduced mechanical ventilation days (WMD - 4.34, 95% CI - 6.98, - 1.69; p < 0.01; I2 = 87%; GRADE: very low; PI - 13.51, 4.84); length of intensive care unit stay (WMD - 4.62, 95% CI - 7.19, - 2.05; p < 0.01; I2 = 78%; GRADE: low; PI - 12.86, 3.61) and the incidence of pneumonia (RR 0.50, 95% CI 0.31, 0.81; p = 0.005; I2 = 54%; GRADE: moderate; PI 0.13, 1.91). No difference in mortality (RR 0.56, 95% CI 0.19, 1.65; p = 0.27; I2 = 23%; GRADE: moderate; PI 0.04, 7.25), length of hospital stay (WMD - 5.39, 95% CI - 11.38, - 0.60; p = 0.08; I2 = 89%; GRADE: very low; PI - 11.38, 0.60), or need for tracheostomy (RR 0.59, 95% CI 0.34, 1.03; p = 0.06; I2 = 54%; GRADE: moderate; PI 0.11, 3.24) was found. CONCLUSIONS: Our results suggest that surgical treatment is advantageous compared to non-surgical treatment for patients with flail chest secondary to rib fractures.

The effects of magnesium sulfate added to epidurally administered local anesthetic on postoperative pain: a systematic review.

BACKGROUND: This study evaluated the efficacy of epidurally administered magnesium associated with local anesthetics on postoperative pain control. METHODS: The study protocol was registered in PROSPERO as CRD42021231910. Literature searches were conducted on Medline, Cochrane, EMBASE, CENTRAL, and Web of Science for randomized controlled trials comparing epidural administration of magnesium added to local anesthetics for postoperative pain in elective surgical adult patients. Primary outcomes were the time to the first Postoperative (PO) Analgesic Request (TFAR), 24-hour postoperative opioid consumption, and Visual Analog Scale (VAS) scores at the first six and 24 postoperative hours. Secondary outcomes included Postoperative Nausea and Vomiting (PONV), pruritus, and shivering. Quality of evidence was assessed using GRADE criteria. RESULTS: Seventeen studies comparing epidural were included. Effect estimates are described as weighted Mean Differences (MD) and 95% Confidence Intervals (95% CI) for the main outcomes: TFAR (MD = 72.4 min; 95% CI = 10.22-134.58 min; p < 0.001; I2 = 99.8%; GRADE: very low); opioid consumption (MD = -7.2 mg (95% CI = -9.30 - -5.09; p < 0.001; I2 = 98%; GRADE: very low). VAS pain scores within the first six PO hours (VAS) (MD = -1.01 cm; 95% CI = -1.40-0.64 cm; p < 0.001; I2 = 88%; GRADE: very low), at 24 hours (MD = -0.56 cm; 95% CI = -1.14-0.01 cm; p = 0.05; I2 = 97%; GRADE: very low). CONCLUSIONS: Magnesium sulfate delayed TFAR and decreased 24-hour opioid consumption and early postoperative pain intensity. However, imprecision and inconsistency pervaded meta-analyses, causing very low certainty of effect estimates.

Efficacy of postoperative analgesia with duloxetine in posthemorrhoidectomy pain: a prospective, randomized, double-blind and placebo-controlled trial.

BACKGROUND: To evaluate the effect of duloxetine when added to a multimodal analgesia regimen on posthemorrhoidectomy pain, opioid consumption, and side effects. METHODS: Prospective, randomized, double-blind placebo-controlled trial. This study included 62 patients who underwent hemorrhoidectomy. The patients were randomly assigned to receive oral duloxetine 60 mg or placebo 2 h before and 24 h after surgery. The primary outcomes were pain intensity - measured on an 11-point visual analog pain scale - and cumulative morphine consumption at 12, 24, and 48 postoperative hours. RESULTS: Fifty-two patients completed the study (25 in the duloxetine group and 27 in the placebo group). Pain scores did not differ between duloxetine and placebo: 4.5; 3.0 - 7.0 vs. 5.0; 3.5 - 7.0, p = 0.68 at 12 h, 3.0; 2.0 - 5.0 vs. 3.0; 2.0 - 5.0, p = 0.56 at 24 h, and 2.5; 1.75 - 3.75 vs. 1.5; 0.5 - 3, p = 0.08 at 48 h. Further, cumulative morphine consumption did not differ between the duloxetine and placebo groups: 4; 1.25 - 10.75 mg vs. 7; 1.0 - 12.0 mg, p = 0.68 at 12 h, 9.5; 2.0 - 17.5 mg vs. 8.0; 4.0 - 18.0 mg; p = 0.80 at 24 h, and 11.0; 2.0 - 27.0 mg vs. 10; 4.0 - 24.0 mg, p = 0.78 at 48 h. Side effects did not differ between the groups. CONCLUSIONS: Compared with placebo, duloxetine did not decrease pain intensity or morphine consumption during the first 48 h postoperatively. TRIAL REGISTRATION: The study was retrospectively registered on the Brazilian Clinical Trials Registry (identifier: RBR-9pdgms, registration date: 08/10/2020).

The effects of a short-term perioperative duloxetine treatment on post-colectomy pain: A randomized, controlled clinical trial.

STUDY OBJECTIVE: To test the hypothesis that duloxetine reduces postoperative morphine consumption and pain intensity in patients undergoing major colonic surgeries. DESIGN: Single-center, prospective, double-blinded, randomized, controlled trial. SETTING: Tertiary university hospital, from December 2019 to September 2021. PATIENTS: Sixty 18-85 years old, ASA I - III patients undergoing elective open major colonic surgeries were randomly allocated into duloxetine (duloxetine) or placebo (placebo) groups (n = 30 per group). INTERVENTIONS: Duloxetine 60 mg or placebo was administered orally 2 h before and 24 h after surgery. MEASUREMENTS: PCA morphine consumption, surgical pain at rest, and movement measured on 10-cm visual analog scales (VAS), Ramsay sedation scores, and the incidence of adverse effects potentially associated with duloxetine were assessed at patients' admission to the post-anesthesia care unit (PACU), 6, 24, and 48 h postoperatively (PO). MAIN RESULTS: After adjusting for age, BMI, ASA physical status, education level, and incision type, no differences were found between groups in PCA morphine consumption 24 PO h (duloxetine = 5.44 ± 2.06 mg; placebo = 10.33 ± 2.06 mg, p = 0.62) or 48 h PO (duloxetine = 9.18 ± 2.06 mg, placebo = 12.93 ± 2.06, p = 1). Pain at rest also did not differ between groups at 24 h PO (duloxetine = 1.76 ± 0.67 cm; placebo = 1 ± 0.67 cm, p = 1) or at 48 h PO (duloxetine = 0.84 ± 0.67 cm; placebo = 0.49 ± 0.67 cm, p = 1). Similarly, groups did not differ regarding pain on movement at 24 h PO (duloxetine = 2.09 ± 0.68 cm; placebo = 1.80 ± 0.68, p = 1) or at 48 h PO (duloxetine = 1.16 ± 0.68 cm; placebo = 0.88 ± 0.68 cm, p = 1). Sedation scores and adverse effects also did not differ between groups. CONCLUSION: Under this study's conditions, short-term duloxetine did not reduce total opioid consumption or pain intensity during the initial 48 h following major colon surgery.

Acute pain consult and management is associated with improved mortality in rib fracture patients.

INTRODUCTION: Traumatic rib fractures result in significant patient morbidity and mortality, which increases with patient age and number of rib fractures. A dedicated acute pain service (APS) providing expertize in multimodal pain management may reduce these risks and improve outcomes. We aimed to test the hypothesis that protocolized APS consultation decreases mortality and morbidity in traumatic rib fracture patients. METHODS: This is a retrospective observational, propensity-matched cohort study of adult patients with trauma with rib fractures from 2012 to 2015, at a single, large level 1 trauma center corresponding to introduction and incorporation of APS consultation into the institutional rib fracture pathway. Using electronic medical records and trauma registry data, we identified adult patients presenting with traumatic rib fractures. Patients with hospital length of stay (LOS) ≥2 days were split into two cohorts based on presence of APS consult using 1:1 propensity matching of age, gender, comorbidities and injury severity. The primary outcome was difference in hospital mortality. Secondary outcomes included LOS and pulmonary morbidity. RESULTS: 2486 patients were identified, with a final matched cohort of 621 patients receiving APS consult and 621 control patients. The mortality rate was 1.8% among consult patients and 6.6% among control patients (adjusted OR 0.25, 95% CI 0.13 to 0.50; p=0.001). The average treatment effect of consult on mortality was 4.8% (95% CI 1.2% to 8.5%;. p<0.001). APS consultation was associated with increased intensive care unit (ICU) LOS (1.19 day; 95% CI 0.48 to 1.90; p=0.001) and hospital LOS (1.61 days; 95% CI 0.81 to 2.41 days; p<0.001). No difference in pulmonary complications was observed. DISCUSSION: An APS consult in rib fracture patients is associated with decreased mortality and no difference in pulmonary complications yet increased ICU and hospital LOS.

Duloxetine for the treatment acute postoperative pain in adult patients: A systematic review with meta-analysis.

BACKGROUND: Duloxetine administered during the acute perioperative period has been associated with lesser postoperative pain and analgesic consumption. STUDY OBJECTIVES: The study aimed to quantify the pooled effects of duloxetine on postoperative pain, analgesic consumption, and side-effects in the first 48 postoperative (PO) hours. DESIGN: Systematic review with meta-analysis. SETTING: Postoperative pain management. PATIENTS: Adult patients undergoing elective surgery. Search strategy and study selection. Medline, Cochrane, EMBASE, CENTRAL, and Web of Science were searched without language restrictions for prospective, parallel randomized controlled trials comparing duloxetine to placebo for the management of postoperative pain in adult patients. MEASUREMENTS: Pain scores (11-point scales), opioid consumption (i.v. morphine equivalents), and frequency of side-effects were compared between duloxetine and placebo. Effect sizes were summarized as mean differences (MD), standardized mean differences (SMD) or risk ratios (RR) with the respective 95% confidence intervals (95% CI). Grading of Recommendations Assessment, Development, and Evaluation (GRADE) criteria were used to classify the quality of evidence. RESULTS: Thirteen studies were included. Duloxetine decreased pain at 24 h (MD = -0.66 points; 95% CI = -1.14 to -0.19 points; SMD = -0.59; 95% CI = -1.06 to -0.12; p = 0.01; I2 = 88%), and at 48 PO hours (MD = -0.90 points; 95% CI = -1.54 to -0.26 points; SMD = -0.66; 95% CI = -0.94 to -0.38; p = 0.01; I2 = 93%); and opioid consumption at 24 PO hours (MD = -8.21 mg; 95% CI = -13.32 mg to -3.10 mg; SMD = -2.17; 95% CI = -3.10 to -1.24; p < 0.001; I2 = 95%), and at 48 PO hours (MD = 7.71 mg; 95% CI = -13.86 mg to -1.56 mg; SMD = -2.13; 95% CI = -3.51 to -0.75; p = 0.02; I2 = 97%). Duloxetine did not affect the prevalence of postoperative nausea and/or vomiting (PONV) pruritus, headache or dizziness. High inter-study heterogeneity and within-study bias resulted in very-low quality of evidence for the primary outcomes. CONCLUSIONS: Although statistically significant effects of duloxetine were found on postoperative pain and opioid consumption during the first 48 postoperative hours, the effect sizes were below the expected minimal clinically relevant differences. Also, high risk-of-bias and inter-study heterogeneity caused the very-low quality of evidence (GRADE). We conclude that the currently available evidence does not support the clinical use of duloxetine for the management of acute postoperative pain.

The Effect of High-Frequency, Structured Expert Feedback on the Learning Curves of Basic Interventional Ultrasound Skills Applied to Regional Anesthesia.

BACKGROUND: Proficiency in needle-to-ultrasound beam alignment and accurate approach to structures are pivotal for ultrasound-guided regional anesthesia. This study evaluated the effects of high-frequency, structured expert feedback on simulation training of such abilities. METHODS: Forty-two subjects randomly allocated as controls or intervention participated in two 25-trial experiments. Experiment 1 consisted of inserting a needle into a bovine muscular phantom parallel to the ultrasound beam while maintaining full imaging of the needle. In experiment 2, the needle aimed to contact a target inside the phantom. Intervention subjects received structured feedback between trials. Controls received a global critique after completing the trials. The slopes of the learning curves derived from the sequences of successes and failures were compared. Change-point analyses identified the start and the end of learning in trial sequences. The number of trials associated with learning, the number of technical errors, and the duration of training sessions were compared between intervention and controls. RESULTS: In experiment 1, learning curves departed from 73% (controls) and 76% (intervention) success rates; slopes (standard error) were 0.79% (0.02%) and 0.71% (0.04), respectively, with mean absolute difference of 0.18% (95% confidence interval [CI], 0.17%-0.19%; P = 0). Intervention subjects' learning curves were shorter and steeper than those of controls. In experiment 2, the learning curves departed from 43% (controls) and 80% (intervention) success rates; slopes (standard error) were 1.06% (0.02%) and 0.42% (0.03%), respectively, with a mean difference of 0.65% (95% CI, 0.64%-0.66%; P = 0). Feedback was associated with a greater number of trials associated with learning in both experiment 1 (mean difference, 1.55 trials; 95% CI, 0.15-3 trials; P = 0) and experiment 2 (mean difference, 4.25 trials; 95% CI, 1.47-7.03 trials; P = 0) and a lower number of technical errors per trial in experiments 1 (mean difference, 0.19; 95% CI, 0.07-0.30; P = .02) and 2 (mean difference, 0.58; 95% CI, 0.45-0.70; P = 0), but longer training sessions in both experiments 1 (mean difference, 9.2 minutes; 95% CI, 4.15-14.24 minutes; P = .01) and 2 (mean difference, 7.4 minutes; 95% CI, 1.17-13.59 minutes; P = .02). CONCLUSIONS: High-frequency, structured expert feedback compared favorably to self-directed learning, being associated with shorter learning curves, smaller number of technical errors, and longer duration of in-training improvement, but increased duration of the training sessions.

Evaluating the depth of the epidural space with the use of ultrasound.

BACKGROUND AND OBJECTIVES: The objective of the present study was to evaluate the use of the ultrasound on the determination of the depth of the epidural space. METHODS: Sixty patients were included in this prospective study; the L(3)-L(4) space was initially identified by palpation followed by the ultrasound measuring the depth of the epidural space (PU). After the epidural puncture the measurements o the depth (PA) were recorded. The data underwent descriptive statistics, and the concordance correlation coefficient and Bland-Altman analysis, with 95% confidence interval were calculated. RESULTS: Analysis of concordance between the palpation and ultrasound methods was 86.6%. Mean values of PU obtained were 4.97 +/- 0.51 cm and PA 4.97 +/- 0.71 cm, and Pearson correlation coefficient of 0.66 while Bland-Altman analysis revealed a mean difference of 0.0035 +/- 0.53 cm with 95% confidence interval between -0.228 and 0.221. CONCLUSIONS: The ultrasound is a precise tool to determine the depth of the epidural space.

Prevalence and predictive factors of urinary retention assessed by ultrasound in the immediate post-anesthetic period.

BACKGROUND AND OBJECTIVES: Urinary retention is a common condition in the post-anesthetic care unit (PACU). Vesical overdistension and consequent damage of the detrusor muscle of the urinary bladder represent situations that can be prevented. The ultrasound allows the reliable measurement of the urinary volume, determining the prevalence of postoperative vesical distension. The objective of the present study was to determine the prevalence of postoperative urinary retention and identify independent predictive factors. METHODS: Two-hundred and fifty-seven patients admitted to the PACU were included prospectively in this study. Parameters collected included: age, gender, physical status, site of surgery, type of anesthesia, time of the surgery and anesthesia, use of opioids, volume of fluids administered, and history of urinary symptoms. Vesical volumes were measured by ultrasound after admission and upon discharge from the PACU. The criteria to characterize urinary retention were: vesical volume equal or higher than 600 mL associated with incapacity of spontaneous micturition for 30 minutes after the diagnosis. Univariate and multivariate analyses were used to indentify independent predictive factors. RESULTS: Urinary retention was observed in 19 patients (7.39%), independent predictive factors identified included urinary volume equal to or greater than 360 mL upon admission to the PACU (Mantel-Haenszel Chi-square test (1 dF) = 18.76; p < 0.01), with an odds ratio of 9.82 (95% confidence interval = 3.26-29.55) and surgeries of the lower limbs (Mantel-Haenszel Chi-square test (1 dF) = 5.33; p = 0.02), with odds ratio of 4.33 (95% confidence interval = 1.34-14.02). CONCLUSIONS: Due to the prevalence of urinary retention, we suggest that a systematic evaluation of the urinary volume at the PACU should be done, especially in those patients with predictive factors.

Using the Cusum curve to evaluate the training of orotracheal intubation with the Truview EVO2 laryngoscope.

BACKGROUND AND OBJECTIVES: Learning curves have proved to be useful tools to monitor the performance of a worker on a new assignment. Those curves have been used to evaluate several medical procedures. The objective of this study was to evaluate the learning of orotracheal intubation (OTI) with the Truview EVO2 laryngoscope with the CUSUM learning curve. METHODS: Four trainees underwent OTI training with the Truview EVO2 laryngoscope in a mannequin. They received orientation on the successful and failure criteria of OTI and alternated during the attempts, for a total of 300 OTI for each one. Four learning curves were plotted using the CUSUM cumulative addition method. RESULTS: It was calculated that the 105 OTIs were necessary to achieve proficiency. The four trainees crossed the line of acceptable failure rate of 5% before completing 105 OTIs; the first trainee reached proficiency after 42 OTIs, the second and third after 56 OTIs, and the fourth after 97 OTIs, and from then on their performance remained constant. Differences in the success rate between residents and experienced anesthesiologists were not observed. CONCLUSIONS: The CUSUM learning curve is a useful instrument to demonstrate objectively the ability when performing a new task. Laryngoscopy with the Truview EVO2 in a mannequin proved to be an easy procedure for physicians with prior experience in OTI; however, one should be cautious when transposing those results to clinical practice.

The attitude of anesthesiologists and anesthesiology residents of the CET/SBA regarding upper and lower limb nerve blocks.

BACKGROUND AND OBJECTIVES: The use of regional blocks especially peripheral nerve blocks (PNB) has been increasing in anesthesiology due to the reduced need to manage the airways, lower cost, and excellent postoperative analgesia. However, its use has restrictions due to the lack of training, that it takes longer to be done, fear of neurological complications, and systemic toxicity. The objective of this study was to measure the attitude of anesthesiologists and anesthesiology residents at Teaching and Training Centers (CET/SBA) regarding PNBs. METHODS: A 25-item questionnaire was developed and it was available, via the Internet and by mail, to those responsible for the 80 CETs, their instructors and residents. RESULTS: Forty-two CETs (52.5%) returned 188 questionnaires, 62 (32%) from anesthesiology residents and 126 (68%) from anesthesiologists. The Cronbach's alpha coefficient of the questionnaire was 0.79. Factor analysis revealed six factors that explain 53% of scores variance: factor 1 - positive attitude, responsible for 18.34% of the variance; factor 2 - training/use, responsible for 11.73% of the variance; factor 3 - negative aspects, responsible for 7.11% of the variance; factor 4 - limiting factors, responsible for 6.39% of the variance; and factor 5 - regional block as a competence differential, responsible for 5.79% of the variance; and factor 6 - respect for the patient, responsible for 5.4% of the variance. CONCLUSIONS: The questionnaire proved to be a reliable tool to measure the attitude regarding regional blocks. Anesthesiologists demonstrated greater interest for patient-related aspects, while the main focus of residents was the acquisition of technical abilities.

Learning curves and mathematical models for interventional ultrasound basic skills.

BACKGROUND: We aimed to construct learning curves and mathematical learning models for ultrasound basic skills: optimizing needle-ultrasound beam alignment and reaching a target inside a phantom. METHODS: Thirty subjects participated in the study. Each subject performed 25 trials. Linear ultrasound probes and a bovine muscular phantom were used. In Experiment 1, subjects tried to insert a needle parallel to the ultrasound beam with full imaging of the needle. For Experiment 2, a segment of tendon was inserted longitudinally into the phantom at a depth of 1 to 1.5 cm. Subjects tried to insert the needle until contacting the tendon. Learning curves were constructed using the cumulative sum (cusum) method. Bush and Mosteller's mathematical learning models were constructed for each skill. RESULTS: Only 30% and 11% of subjects attained proficiency in Experiments 1 and 2, respectively. The predicted average numbers of trials to achieve 95% success rates as estimated from Bush and Mosteller's models were 37 and 109, respectively. CONCLUSIONS: Learning interventional ultrasound basic skills may require a considerable number of trials. Cusum charts revealed that individuals acquire such abilities at variable rates. As skills were assessed in phantoms, our results do not apply to blocks given to real patients.

Comparison of the plasma levels of 50% enantiomeric excess (S75/R25) 0.5% bupivacaine combined with 1:200,000 epinephrine between the parasacral and infragluteal sciatic nerve blocks.

BACKGROUND AND OBJECTIVES: Local anesthetics (LA) are safe drugs when the proper dose and localization are used. The rate of absorption of the local anesthetic depends on its mass and blood flow at the site of the injection. The objective of this study was to analyze the plasma concentration of 50% enantiomeric excess (S75R25) 0.5% bupivacaine combined with 1:200,000 epinephrine in the parasacral (PS) and infragluteal (IG) sciatic nerve block (SNB). METHODS: Twenty-eight patients scheduled for ankle and foot surgeries were randomly divided into two groups in this prospective study. In Group 1, SNB was performed with IG neurostimulation, while in Group 2 the PS method was used. Both groups received 30 mL of 0.5% bupivacaine (S75/R25) with 1:200,000 epinephrine. Arterial blood samples, 5 mL, were drawn at 0, 15, 30, 60, and 90 minutes after the administration of the LA. High-performance liquid chromatography was used to analyze the serum concentrations. Demographic data of both groups were compared using the Student t test for independent samples and Fisher's Exact test. Bifactorial Analysis of Variance for repeated samples was used for the data concerning the plasma concentrations. RESULTS: Groups 1 and 2 showed no significant demographic differences. The maximal concentration (Cmax) in Group 1 (308 +/- 91 ng.mL(-1)) was obtained in samples number 5 (90 minutes), while in Group 2 (425 +/- 280 ng.mL(-1)) it was obtained in samples number 2 (15 minutes). Cases of systemic toxicity were not observed. CONCLUSIONS: Cmax of 0.5 % bupivacaine (S75/R25) with 1:200,000 in the parasacral approach was higher when compared with the infragluteal SNB.